1. Field of the Invention
The present invention relates to a power supply system for a field device connected to a wire-line network with a radio module. More particularly, the present invention provides a power supply system for a field device with a radio module configured for data communication with an external unit.
2. Description of the Related Art
In industrial automation, field devices are used to detect and/or set process variables. Such devices are generally connected via field bus systems (such as HART, PROFIBUS Fieldbus Foundation). The process wiring of such field devices is done at least via a two-wire line, through which the power supply of the field device comes, in addition to the data communication. The wire-line data communication can also be realized as wireless data communication, while more modem field devices are being produced with integrated radio modules, including a power source, and thus can also be operated as stand-alone units.
In order for field devices without a radio module, i.e., those which only have a communication and power supply interface, to be able to operate with a radio module (wireless module), the problem is that such a radio module cannot be supplied with energy by the field device. Therefore, such a radio module must either have its own power supply or the power supply must be wire-line type.
Thus, for example, a field device is known from DE 10 2009 047 538 A1, the entire contents of which are incorporated herein by reference, can be operated as a radio field device by outfitting it with a radio module. For this, the radio module is connected via the communication interface of the field device with the device itself and it has its own power supply source by which the field device is also supplied with energy.
In this way, a wire-line network built from several field devices can be retrofitted to a radio network, in which case the existing wire-line network is no longer needed thanks to such a conversion to a radio network.
But if not all field devices of a wire-line network can be converted or need to be converted, the method known from DE 10 2009 047 538 A1 is not applicable.
Furthermore, DE 10 2007 015 203 A1, the entire contents of which are also incorporated herein by reference, describes a wireless automation system in which a base station communicates wirelessly with several slave modules, while one slave module is connected by wireless or wire-line manner with several field devices as a sensor/actuator distributor. This sensor/actuator distributor has a wireless power supply that comes via an inductive coupling.
Finally, DE 20 2004 021 004 U1, the entire contents of which are incorporated herein by reference, proposes inductively withdrawing energy via a multistrand cable for the power supply of a field device.
Accordingly, there is a need for an improved power supply system for a field device with a radio module sufficient to overcome at least one of the detriments noted above.